Abstract
Araujia sericifera is an invasive plant with an increasing presence in South East Spain, where it produces damage to native trees and shrubs and citric orchards. As the climatic conditions in the study area are becoming harsher due to the climate change, the stress tolerance of this species has been studied during germination and vegetative growth. Growth parameters, photosynthetic pigments, ion accumulation, and antioxidant mechanisms were analysed in plants that were subjected to water deficit and salt stress. Seed germination was reduced by salinity but 50% of the seeds still germinated at 50 mM NaCl. The ungerminated seeds did not lose their germination capacity as shown in ‘recovery’ germination assays in distilled water. Germination was less affected by osmotic stress that was induced by polyethylene glycol (PEG), and germination velocity increased in the recovery treatments after exposure to NaCl or PEG. Plant growth was practically unaffected by 150 mM NaCl but inhibited by higher NaCl concentrations or severe drought stress. Nevertheless, all the plants survived throughout the experiment, even under high salinity (600 mM NaCl). A. sericifera relative stress tolerance relies, at least to some extent, on effective antioxidant mechanisms that are based on flavonoid biosynthesis and the activation of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, and glutathione reductase.
Highlights
Biological invasions, accentuated by global warming [1,2], are a major environmental threat and cause significant economic losses [3]
As drought and secondary salinisation are enhanced by global warming and are becoming more frequent in the Mediterranean area, we aimed to study the responses to these two types of abiotic stresses in this invasive species
The seeds germinated within two weeks in a percentage of 86% under the control conditions, whereas only 50% of the seeds germinated under 50 mM NaCl
Summary
Biological invasions, accentuated by global warming [1,2], are a major environmental threat and cause significant economic losses [3]. The number of studies on the responses of invasive plant species to environmental stress factors has increased in the last decades [5,6,7,8,9,10]. Abiotic stress tolerance in plants is based on several mechanisms that ensure survival under drought, salinity, or extreme temperature conditions. Abiotic stress is associated with oxidative stress that is produced by the accumulation of reactive oxygen species (ROS) and causes significant damage to plants, including DNA damage and cellular death [13]. Drought, or salinity are environmental conditions that can increase the concentration of these molecules within plant cells [13]. Antioxidant systems’ nature varies from enzymes and other proteins to non-enzymatic compounds such as carotenoids, vitamins, flavonoids, or other phenolic compounds [13,16,17]
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